orthorhombic Oxides
Alexandrite
BeAl2O4:Cr
Quick Facts
Hardness
8.5
Specific Gravity
3.71
Refractive Index
1.746
Optical Character
Biaxial +
Crystal Structure
#! Species: Alexandrite (Chrysoberyl)
#! System: Orthorhombic (mmm)
#! Habit: Prismatic with colour-change phenomenon
orthorhombic[mmm]:{110}@1.0 + {010}@0.6 + {111}@0.4 | phenomenon[colour_change]
orthorhombic
mmm
{110} {010} {111}
Physical Properties
Crystal Systemorthorhombic
Hardness (Mohs)8.5
Specific Gravity3.71
CleavageGood in one direction
FractureConchoidal to uneven
LustreVitreous
Optical Properties
Refractive Index1.746
Birefringence0.008-0.010
Optical CharacterBiaxial +
Dispersion0.015
Pleochroismstrong: Green / Orange-yellow / Red-purple (Three distinct pleochroic colours visible through dichroscope; separate from colour-change)
FluorescenceWeak red (LWUV)
Colours
Green to blue-green (daylight)Red to purple-red (incandescent)Yellow-green
Localities
Russia (Urals)BrazilSri LankaTanzaniaIndia
Common Inclusions
Silk (needle inclusions)FingerprintsCyclic twin planesCrystal inclusionsNegative crystals
Crystal Forms
prismpinacoid
Diagnostic Features
Colour change (daylight green to incandescent red); strong pleochroism (three colours)
Interactive Preview
Open this crystal in the CDL Playground to rotate, export, and explore in 3D.
Open in Playground #! Species: Alexandrite (Chrysoberyl)
#! System: Orthorhombic (mmm)
#! Habit: Prismatic with colour-change phenomenon
orthorhombic[mmm]:{110}@1.0 + {010}@0.6 + {111}@0.4 | phenomenon[colour_change]
Synthetics & Simulants
Known synthetic and simulant versions of Alexandrite
Related Minerals
Other minerals in the orthorhombic system
